Json wrapped array deserialization

Question

I've been trying to deserialize the following Json file using the wrapper method from this answer: Serialize and Deserialize Json and Json Array in Unity. Deserializing the base objects and their normal variables into a list of objects works fine, but I can't figure out how to get the "tags" array into a normal string array within the deserialized game object, since it will have a variable number of indices.

 {
     "Items" : [
         {
             "ID": 0,
             "title": "Mage Hand",
             "description": "A simple spell used to manipulate objects through telekinesis.",
             "texture": "/Textures/Cards/Spells/ArcaneSpell01.mat",
             "type" : "SPELL",
             "tags": [ 
                 {"primary" : "arcane"} ,
                 {"primary_strength" : "1"} ,
                 {"secondary" : "force"} ,
                 {"secondary_strength" : "1"}
             ]
         },
         {
             "ID": 1,
             "title": "A Colleague",
             "description": "Another practicioner of the arcane arts. Perhaps they know something useful?",
             "texture": "/Textures/Cards/Contacts/Wizard01.mat",
             "type" : "CREATURE",
             "tags": [ 
                 {"primary" : "arcane"} ,
                 {"primary_strength" : "1"} ,
                 {"secondary" : "relationship"} ,
                 {"secondary_strength" : "1"}
             ]
         }
     ]
 }

Any help is greatly appreciated :)

Answer 1

Answer by Bunny83 · Aug 23, 2019 at 10:31 PM

The objects in your tags array are not the same kind of objects since the variable / field names are different. This makes it difficult / impossible to actually map the json objects to C# objects. Since json does not contain any type information for objects, deserialization can not differentiate between different class types.

It might be easier to not map them to specific C# classes but to use a generic json library like my SimpleJSON library. It can handle any kind of json structure. It provides a simple hierachical structure to access any information stored in the json text.

If you don't want to use such a library you might want to rethink about the json structure. A tag object might look like this:

 {
     "name":"primary",
     "value":"arcane"
 }

instead of

 {
     "primary" : "arcane"
 }

This way you can model any kind of "tags" and use the same C# class for all tags. If you only have those 4 tags you probably don't want to use an array at all and use a tags class. For those 4 tags I would probably do something like:

 "tags": {
     "primary": {
         "type": "arcane",
         "strength": "1"
     },
     "secondary": {
         "type": "force",
         "strength": "1"
     }
 }

Though since we don't know the exact usecase we can't decide for you.

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QuinnForTheWin · Aug 28, 2019 at 04:00 PM 0

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Thank you very much for the clarification! The only thing I'm worried about with using a tag object is that I'm expecting to have a variable number of tags for each item. I can understand having a tag object that has the variables "type" and "strength", but I'm still unclear how to parse my individual items as having a variable number of tag objects within them without using an array. Is that something that is even possible without using a supplementary library such as the one you provided?

Bunny83 QuinnForTheWin · Aug 28, 2019 at 05:35 PM 0

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No, that's not possible without such a library since Unity's json serializer is only an object mapper. Objects in C# are statically defined and you can not add / remove variables / fields at runtime.

Apart from that Unity does not support inheritance / polymorphism for sub classes since there's no type information inside the json data so the deserializer does not know which object it should use to represent a certain object. Sub classes are always created based on the field type and therefore an array can only contain one type of objects.

Json wrapped array deserialization

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